Negative resist composition comprising hydroxy-substituted base polymer and si-containing crosslinker having epoxy ring and a method for patterning semiconductor devices using the same

ABSTRACT

A negative resist composition and a method for patterning semiconductor devices using the composition are provided. The negative resist composition contains an alkali-soluble hydroxy-substituted base polymer, a silicon-containing crosslinker having an epoxy ring, and a photoacid generator. In the method for patterning semiconductor devices, fine patterns are formed according to a bi-layer resist process using the negative resist composition.

BACKGROUND OF THE INVENTION

This application claims priority to Korean Patent Application No.2002-34624, filed on Jun. 20, 2002, the disclosure of which isincorporated herein by reference.

1. Field of the Invention

The present invention relates to a silicon-containing photoresistcomposition and a method for patterning a semiconductor device. Moreparticularly, the present invention relates to a silicon-containingnegative resist composition suitable for use in a bi-layer resistprocess, and a method for patterning semiconductor devices using thesame.

2. Discussion of the Related Art

As the manufacture of semiconductor devices becomes more complicated andsemiconductor devices become more highly integrated, there is a need toform fine patterns. Furthermore, with regard to 1-Gigabit or moresemiconductor devices, a pattern size having a design rule of 0.2 μm orless is needed. Therefore, the use of conventional photoresist materialsfor KrF eximer laser (248 nm) is limited. For this reason, lithographytechniques using ArF eximer laser (193 nm) or F₂ eximer laser (157 nm),which are shorter-wavelength energy sources than KrF eximer laser, haveemerged. Lithography processes using F₂ eximer laser (157 nm) needresist materials having a new structure.

However, ArF and F₂ resist materials have many problems due to theirstructural limitations as compared with i-line or KrF resist materials,which include pattern collapse due to the fine pattern size and poorresistance to dry etching. Therefore, there is a need to develop newresist materials and processes therefor.

In a photolithography process for manufacturing highly integratedsemiconductor devices, the application of a bi-layer resist (BLR)process improves characteristics such as dry-etching resistance andformation of high aspect ratio patterns.

In the BLR process, binary chemically amplified resists composed of asilicon-containing polymer having in its backbone silicon atomsubstituents and a photoacid generator, e.g., positive chemicallyamplified resists, have been widely used. Also, the development ofhighly sensitive resist materials for BLR processes using ashort-wavelength light source has focused on positive chemicallyamplified resists. However, silicon-containing resist compositionsdeveloped to date for BLR processes have strong hydrophobicity andexhibit poor adhesion to the underlying layer. Also, it is difficult tocontrol the amount of silicon to an appropriate level for resistmaterials.

The use of positive resists is limited in forming isolated patterns forhigh-speed, high-performance DRAMs. A lithography process formanufacturing 1-Gigabit or more DRAMs necessitates the use of a phaseshift mask. In designing phase shift masks, using negative resists ismore advantageous than using positive resists. Therefore, a need existsfor developing negative resists which are highly transparent withrespect to an exposure light source having a short wavelength, andexhibit high resolution and have a high resistance to dry-etching.

SUMMARY OF THE INVENTION

One aspect of the invention provides a negative resist compositionhaving high transmittance in a short-wavelength region, and a highdry-etching resistance as it contains silicon. In addition, the negativeresist composition can be effectively used in bi-layer resist (BLR)processes to secure a high resolution and a high aspect ratio.

The invention also provides a method for forming fine patterns having ahigh aspect ratio required for highly integrated semiconductor devices.

According to an embodiment of the present invention, the inventionprovides a negative resist composition comprising: an alkali-solublehydroxy-substituted base polymer, a silicon-containing crosslinkerhaving an epoxy ring, and a photoacid generator (PAG).

In the negative resist composition according to an embodiment of thepresent invention, the base polymer can be a Novolac resin partially orfully substituted with a hydroxy group.

The base polymer can be polyhydroxystyrene, and preferably,poly(2-hydroxystyrene), poly(3-hydroxystyrene), orpoly(4-hydroxystyrene).

The base polymer comprises a (meth)acrylate repeating unit having ahydroxy group, and preferably, a 2-hydroxyethyl(meth)acrylate repeatingunit or 3-hydroxypropyl(meth)acrylate repeating unit.

In the negative resist composition according to another embodiment ofthe present invention, the silicon-containing crosslinker can be adiglycidyl ether-terminated poly(dimethylsiloxane)oligomer or polymer.For example, the silicon-containing crosslinker can have the followingformula:

where n is an integer from 5 to 1000.

It is preferable that the silicon-containing crosslinker have amolecular weight of about 300 to about 30,000 and that the amount of thesilicon-containing crosslinker is in the range of about 5.0% to about50% by weight based on the total weight of the polymer base.

In the negative resist composition according to another embodiment ofthe present invention, the amount of the PAG is in the range of about1.0% to about 10% by weight based on the total weight of the basepolymer. The PAG is preferably a triarylsulfonium salt, a diaryliodoniumsalt, or a mixture of the forgoing salts, and more preferably,triphenylsulfonium triflate, diphenyliodonium triflate,di-t-butylphenyliodium triflate, or any combination thereof.

Alternatively, the negative resist composition according to anotherembodiment of the present invention further comprises an organic base.In this case, the amount of the organic base is in the range of about0.01% to about 2.0% by weight based on the content of the PAG. It ispreferable that the organic base be triethylamine, triisobutylamine,trioctylamine, triisodecylamine, triethanolamine, and any combinationthereof.

According to another embodiment of the present invention, the inventionprovides a method for patterning a semiconductor device, in which finepatterns are formed according to a BLR process using the negative resistcomposition according to the embodiments described above. In the method,initially, a first resist layer is formed on a target layer to be etchedon a semiconductor substrate. Next, a second resist layer is formed onthe first resist layer by coating with the first resist layer with anegative resist composition according to the embodiments describedabove. The second resist layer is subjected to pre-baking and exposureprocesses. The exposed second resist layer is baked (post-exposurebaking) and developed into a second resist layer pattern. The firstresist layer is etched using the second resist layer pattern as anetching mask to form a first resist layer pattern. Lastly, the targetlayer is etched using the first resist layer pattern as an etching mask.In the exposure process, a KrF, ArF, or F₂ eximer laser is used.

According to another embodiment of the present invention, a negativeresist composition, as described above, containing a hydroxy-substitutedbase polymer, a silicon-containing crosslinker having an epoxy ring, anda PAG provides good adhesion and wetability to the underlying layer.

According to another embodiment of the present invention, the negativeresist composition is highly transparent in a short-wavelength region,such as the region of light emitted by a KrF, ArF, or F₂ eximer laser,and exhibits a high resolution and a high aspect ratio. Therefore, thenegative resist composition according to the present invention can beeffectively used in BLR processes and in forming fine patterns having ahigh aspect ratio required for highly integrated semiconductor devices.

BRIEF DESCRIPTION OF THE DRAWINGS

The above features and advantages of the present invention will becomemore apparent by describing in detail exemplary embodiments thereof withreference to the attached drawings in which:

FIGS. 1 through 4 are sectional views for illustrating a method forforming patterns in a semiconductor device according to an embodiment ofthe present invention.

DETAILED DESCRIPTION OF THE INVENTION

A negative resist composition according to an embodiment of the presentinvention contains as basic components an alkali-solublehydroxy-substituted base polymer, a silicon-containing crosslinkerhaving an epoxy ring, and a photoacid generator (PAG).

According to another embodiment of the present invention, the negativeresist composition base polymer includes a Novolac resin partially orfully substituted with a hydroxy group and polyhydroxystyrene, such aspoly(2-hydroxystyrene), poly(3-hydroxystyrene), poly(4-hydroxystyrene),and the like. The base polymer has a (meth)acrylate repeating unithaving a hydroxy group, such as a 2-hydroxyethyl(meth)acrylate repeatingunit, 3-hydroxypropyl(meth)acrylate repeating unit, and the like.

The silicon-containing crosslinker includes a diglycidylether-terminated poly(dimethylsiloxane)oligomer or polymer. For example,the silicon-containing crosslinker may have the following formula:

where n is an integer from 5 to 1000.

It is preferable that the silicon-containing crosslinker has a molecularweight of about 300 to about 30,000. The amount of thesilicon-containing crosslinker may be in the range of about 5.0% toabout 50% by weight based on the total weight of the polymer base.

In the negative resist composition according to another embodiment ofthe present invention, the amount of the PAG may be in the range ofabout 1.0% to about 10% by weight based on the total weight of the basepolymer. The PAG includes preferably a triarylsulfonium salt, adiaryliodonium salt, or any combination thereof, and more preferably,triphenylsulfonium triflate, diphenyliodonium triflate,di-t-butylphenyliodium triflate, or any combination thereof.

The negative resist composition according to another embodiment of thepresent invention may further comprise an organic base. In this case,the amount of the organic base is in the range of about 0.01% to about2.0% by weight based on the content of the PAG. It is preferable thatthe organic base be triethylamine, triisobutylamine, trioctylamine,triisodecylamine, triethanolamine, and any combination thereof.

FIGS. 1 through 4 are sectional views for illustrating a method forforming patterns in a semiconductor device according to an embodiment ofthe present invention.

Referring to FIG. 1, a target layer 12 to be etched is formed on asubstrate 10, for example, a semiconductor substrate or a transparentsubstrate. Next, in order to form a bi-layer resist (BLR) layer on thetarget layer 12, a first resist layer 22 is formed on the target layer12 and then a second resist layer 24 having a thickness of about 100 nmto about 500 nm is formed by coating the first resist layer 22 with asilicon-containing negative resist composition by spin coating andpre-baking the coated layer. The second resist layer 24 is formed usingthe negative resist composition according to the present inventiondescribed above. In other words, the second resist layer 24 basicallycontains an alkali-soluble hydroxy-substituted base polymer, asilicon-containing crosslinker having an epoxy ring, and a PAG.

Referring to FIG. 2, a selected region of the second resist layer 24 isexposed through a mask 26 using a KrF, ArF, or F₂ eximer laser, so thatan exposed region 24 a and a non-exposed region 24 b result in thesecond resist layer 24.

Next, the exposed second resist layer 24 is subjected to a post-exposurebaking (PEB) process. As a result, in the exposed region 24 a of thesecond resist layer 24 a cross-linking reaction takes place due to theacid generated from the PAG.

Referring to FIG. 3, the exposed second resist layer 24 is developedusing an alkaline developer solution, such as tetramethylammoniumhydroxide (TMAH) solution, to remove the non-exposed region 24 b andform a second resist layer pattern 24 a, which is a negative pattern ofthe exposed region 24 a.

Referring to FIG. 4, the first resist layer 22 is etched using thesecond resist layer pattern 24 a as an etching mask to form a firstresist layer pattern 22 a. Subsequently, the target layer 12 is etchedinto a desired pattern 12 a using the first resist layer pattern 22 a asan etching mask.

The present invention will be described in greater detail with referenceto the following examples. Various changes can be made in the followingexamples and thus the scope of the invention is not limited to thefollowing examples.

SYNTHESIS EXAMPLE 1 Synthesis of Base Polymer having HydroxyethylMethacrylate Repeating Unit

In a round bottom flask, about 13 g (100 mmol) of 2-hydroxyethylmethacrylate was placed and dissolved in about 40 g of tetrahydrofuran(THF) with an addition of about 0.82 g (5 mol %) ofazobisisobutyronitrile (AIBN). After purging with nitrogen gas, themixture was subjected to polymerization at a temperature of about 65° C.for about 20 hours.

After the polymerisation was completed, the reaction product was slowlyprecipitated in excess n-hexane solution, and the precipitate wasfiltered. The precipitate was dissolved again in an appropriate amountof THF and reprecipitated in n-hexane solution. The resultingprecipitate was dried in a vacuum oven at about 50° C. for about 24hours to obtain a desired polymer with a yield of about 75%.

The resulting polymer had a weight average molecular weight (Mw) ofabout 15,500 and a polydispersity (Mw/Mn) of about 2.0.

SYNTHESIS EXAMPLE 2 Synthesis of Base Polymer having HydroxyethylMethacrylate Repeating Unit and Styrene Repeating Unit

A desired polymer was synthesized with a yield of about 75% in the samemanner as in synthesis example 1 except that about 9.1 g (50 mmol) of2-hydroxyethyl methacrylate and about 3 g (30 mmol) of styrene werepolymerized.

The resulting polymer had an average molecular weight (Mw) of about14,300 and a polydispersity (Mw/Mn) of about 2.1.

SYNTHESIS EXAMPLE 3 Synthesis of Polyhydroxystyrene Base Polymer

About 12 g (0.1 mol) of polyhydroxystyrene (Mw=12,000, Mw/Mn=1.1) andabout 24 g (0.3 mol) of 2-chloroethanol were dissolved in about 100 mLof THF together with 0.12 mol of triethylamine and reacted at reflux forabout 12 hours.

After the reaction was completed, the reaction product was slowlyprecipitated in an n-hexane solution, and the precipitate was filtered.The precipitate was dissolved again in an appropriate amount of THF andreprecipitated in an n-hexane solution. The resulting precipitate wasdried in a vacuum oven at about 50° C. for about 24 hours to obtain adesired polymer with a yield of 80%.

SYNTHESIS EXAMPLE 4

Synthesis of Epoxy Novolac Resin Base Polymer

A desired polymer was synthesized in the same manner as in synthesisexample 3 except that an i-line Novolac resin and 2-chloroethanol wereused.

EXAMPLE 1 Preparation of Resist Composition and its LithographyPerformance

One gram of the polymer synthesized in synthesis example 1, about 0.2 gof crosslinker diglycidyl ether-terminated poly (dimethylsiloxane)(viscosity=15 cSt, Aldrich Chemical Co.), and about 0.02 g of photoacidgenerator triphenylsulfonium triflate were dissolved in about 8 gpropylene glycol methyl ether acetate (PGMEA), followed by an additionof about 1 mg of organic base truisobutylamine to completely dissolvethe materials. The resulting resist solution was filtered using a 0.2μm-membrane filter.

The filtered resist solution was coated on a bare silicon wafer, whichhad been treated with hexamethyldisilazne (HMDS), to a thickness ofabout 0.30 μm, followed by soft backing at about 120° C. for about 90seconds and exposure using an ArF eximer laser stepper (NA=0.6 andσ=0.75).

Next, the wafer with the resist layer was subjected to post-exposurebaking (PEB) at about 120° C. for about 60 seconds and development inabout 2.38% by weight of a tetramethylammonium hydroxide (TMAH) solutionfor about 60 seconds. As a result, a sharp line and space pattern havinga width of about 180 nm was obtained with an exposure dose of about 15mJ/cm².

EXAMPLE 2 Preparation of Resist Composition and its LithographyPerformance

Different photoresist compositions were prepared using about 1 g of eachof the polymers synthesized in synthesis examples 2 through 4 in thesame manner as in example 1, and lithography performance was evaluated.For all of the photoresist compositions, a sharp line and space patternhaving a width of about 180 nm was obtained with an exposure dose ofabout 15 mJ/cm².

As described above, a negative resist composition according to anotherembodiment of the present invention includes an alkali-solublehydroxy-substituted base polymer, a silicon-containing crosslinkerhaving an epoxy ring, and a PAG. In other words, unlike conventionalresist compositions for use in BLR processes, most of which containsilicon atom substituted into the polymer backbone, in the negativeresist composition according to an embodiment of the present inventionsilicon atom is incorporated into the crosslinker. Accordingly, theamount of silicon in the negative resist composition can be more easilycontrolled, and the negative resist composition has a high dry-etchingresistance due to the silicon. In addition, since the negative resistcomposition contains the hydroxy-substituted base polymer and thecrosslinker having an epoxy ring, its adhesion and wetability to theunderlying layer can be easily controlled. The negative resistcomposition according to another embodiment of the present invention ishighly transparent in a short-wavelength region, such as the region oflight emitted by a KrF, ArF, or F₂ eximer laser, and exhibits highresolution and has a high aspect ratio. Therefore, the negative resistcomposition according to the present invention can be effectively usedin BLR processes and in forming fine patterns having a high aspect ratiorequired for highly integrated semiconductor devices.

While the present invention has been particularly shown and describedwith reference to exemplary embodiments thereof, it will be understoodby those of ordinary skill in the art that various changes in form anddetails may be made therein without departing from the spirit and scopeof the present invention as defined by the following claims.

1. A negative resist composition comprising: an alkali-soluble basepolymer substituted with a hydroxy group, wherein the base polymer is aNovolac resin partially or fully substituted with a hydroxy group; asilicon-containing crosslinker having an epoxy ring; and a photoacidgenerator.
 2. The negative resist composition of claim 1, wherein thesilicon-containing crosslinker has a molecular weight of about 300 toabout 30,000.
 3. The negative resist composition of claim 1, wherein theamount of the silicon-containing crosslinker is in the range of about5.0% to about 50% by weight based on the total weight of the basepolymer.
 4. The negative resist composition of claim 1, wherein theamount of the photoacid generator is in the range of about 1.0% to about10% by weight based on the total weight, of the base polymer.
 5. Thenegative resist composition of claim 1, wherein the photoacid generatoris a triarylsulfonium salt, a diaryliodonium salt, or any combinationthereof.
 6. The negative resist composition of claim 5, wherein thephotoacid generator is triphenylsulfonium triflate, diphenyliodoniumtriflate, di-t-butylphenyliodium triflate, or any combination thereof.7. A negative resist composition comprising: an alkali-soluble basepolymer substituted with a hydroxy group; a silicon-containingcrosslinker having an epoxy ring; and a photoacid generator, wherein thebase polymer is a polyhydroxystyrene.
 8. The negative resist compositionof claim 7, wherein the base polymer is poly(2-hydroxystyrene),poly(3-hydroxystyrene), or poly(4-hydroxystyrene).
 9. A negative resistcomposition comprising: an alkali-soluble base polymer substituted witha hydroxy group; a silicon-containing crosslinker having an epoxy ring;and a photoacid generator, wherein the base polymer comprises a(meth)acrylate repeating unit having a hydroxy group.
 10. The negativeresist composition of claim 9, wherein the base polymer comprises a2-hydroxyethyl(meth)acrylate repeating unit or a3-hydroxypropyl(meth)acrylate repeating unit.
 11. A negative resistcomposition comprising: an alkali-soluble base polymer substituted witha hydroxy group; a silicon-containing crosslinker having an epoxy ring;and a photoacid generator, wherein the silicon-containing crosslinker isa diglycidyl ether-terminated poly(dimethylsiloxane)oligomer or polymer.12. The negative resist composition of claim 11, wherein thesilicon-containing crosslinker has the following formula:

where n is an integer from 5 to
 1000. 13. A negative resist compositioncomprising: an organic base polymer substituted with a hydroxy group; asilicon-containing crosslinker having an epoxy ring; and a photoacidgenerator, wherein the silicon-containing crosslinker is a diglycidylether-terminated poly(dimethylsiloxane)oligomer or polymer.
 14. Thenegative resist composition of claim 13, wherein the amount of theorganic base is in the range of about 0.01% to about 2.0% by weightbased on the content of the photoacid generator.
 15. The negative resistcomposition of claim 13, wherein the organic base is selected from thegroup consisting of triethylamine, triisobutylamine, trioctylamine,triisodecylaniine, triethanolamine, and any combination thereof.